Agitation and aeration apparatus



2 Sheets-Sheet 1 S. TUCKER Filed Feb. l5, 1940 MIMHW AGITATION AND AERATION AY'PARATUS April 15, 1941.

April 15, 1941- s. TUCKER 2,238,139

AGITATION AND AERATION APPARATUS Filed Feb. 15, 1940 2 Sheets-Sheet 2 YJ ligne?.

Patented Apr. 15, 1941 y 2.238.139 AGITATION AND AERATION APPARATUS Stanley Tucker, London, England, assignor to Minerals Separation North American Corporation, New York, N. Y., a corporation of Mary-` land Application February l5, 1940. Serial No. 318,988

In Great I i'ltaln March 22, 1939 8 Claims.

This invention comprises improvements in or relating to agitationand aeration apparatus.

The present invention comprises in an agitation and aeration apparatus the combination of an agitation-vessel, a downwardly extending rotatable shaft dipping thereinto, an agitator on the shaft comprising a plurality of liquid-agitating blades and means to supporty the blades from the shaft so that their inner ends are spaced away from the shaft, an annular shield above the blades the central aperture of which surrounds the shaft and is spaced therefrom and a downcast air tube surrounding the shaft with its lower end passing through the shield so that it enters the space within the blades, the diameter of the air tube being such as to allow a liquid-circulation space between the inner periphery of the shield and the outside of the air tube. In this way liquid can be drawn in by the rotating agitator through the space between the air tube and the shield and projected outwardly by the blades due to their centrifugal action.` This maintains a constant circulation of any liquid in which the agitating and aerating apparatus is immersed. At the same time air is drawn down the inside of the air tube and delivered at the bottom there-` of beneath the level of the liquid circulated by the blades. This airmay either be drawn outward beneath the liquid by the blades already described or it may be delivered to a second airinipelling set of blades beneath the first, as may be desired. The effect is that airis driven into the liquid at a level below that of the agitation inducedby the agitator blades and as the air tends to rise in the liquid it is necessarily involved in the zone of agitation and becomes thoroughly broken up and incorporated in the liquid.

The agitator may be disposed in an agitation vessel ynear the bottom thereof. The .blades of the agitator may be shrouded by a disc attached to their undersides. Alternatively they may be unshrouded and work close to the bottom oi the cell.

The following isa description of certain specific forms of agitation and aeration apparatus in ac- The apparatus is illustrated in the accompany ing drawings in which:

Figure 1 is a vertical central section through a portion of froth flotation apparatus in accordance with the invention;

Figure 2 is a sectional plan taken upon the line 2--2 of Figure 1;

Figure 3 is a detail of the agitator illustrated in Figure l;

Figure 4 is a detail .of a modified form of agitator, and

Figure 5 is a detail of a further modification.

Referring to Figures 1 to 3 the apparatus comprises an agitation vessel Ii which in the case i1- lustrated is a froth flotation concentration cell. One such cell may beused or a number of such cells may be arranged side by side as shown in the drawings with intercommunication openings I2 between them. A vertical shaft I3 dips into each of the cells II and supportsat its lower end a disc I44 on which are four inclined agitating blades I5. The upper edges of these blades support a second separating disc IE and upon the disc I6 there are a number, say twelve or sixteen, of upstanding blades Il which are set so that their front faces slope to the rear of a radial line drawn through their inner edges, as best seen by the dotted lines in Figure 2. The inner edges of these agitator blades IlV are spaced a convenient distance, for example four inches in a fifteen-inch impeller. from the axis of the shaft I3. Above theblades I1 there is a flat annular shield I8 of metal which covers over the upper edges of the blades I1 and has an interior diameter in the case stated of about six inches.

Surrounding the shaft I3 and concentric therewith is a downcast air tube I9 of somewhat smaller diameter than the central aperture in the shield I8. The lower end of the air tube I9 is somewhat flared outwardly but not to an extent sufficient to prevent it from passing through the aperture in the shield I8. The air tube I9 is supported in a surrounding tube 2l) which at the upper end is secured to brackets 2l by means of a flange 22. The air tube I9 is made-adjustable in the tube 20 so that its heightcan be varied as desired. The shaft I3 passes upwardly beyond the top of the air tube I9 and is provided with a driving pulley or other means, notshown in the drawings, to permit it to be rotated with a peripheral speed of `1500 to 1800 feet per minute.

In use the air tube I9 is adjusted so that its lower end is spaced somewhat above the middle disc I6 of the agitator. It will be observed that there is a space between the outside ofthe tube I9 and the edge of the aperture in the shield I8. When the agitator is rotated at the peripheral speed as above stated, being immersed in a liquid which lls the cell II, the first effect is to empty the air tube I9 of liquid; thereafter liquid is drawn in through the annular space between the air tube I9 and the shield I8 and is expelled by the agitator blades I1 at the periphery of the agitator. This induces a strong circulation of pulp or other liquid contained in the vessel. Beneath this circulating pulp air is drawn in below the bottom of the air tube and is expelled in a stream with the pulp by the blades I1 and by the lower agitator blades I5. This air is thereby beaten into the pulp. As the air enters the liquid at the under side of the stream or pulp which is drawn in through the space between the shield I8 and the tube I9 it is not only beaten into the pulp but as it rises it enters the stream of pulp and becomes thoroughly incorporated therein.

'I'he height of adjustment of the air tube I9 is a matter of some importance and the best height to meet any particular conditions can readily be ascertained by experiment.

In the vessel II bailies 23 are arranged around the agitator. These consist in the illustration shown of upstanding plates secured to the bottom oi' the vessel, II and disposed radially. Alternatively they may 'be at an inclination to the radius around the shaft. They meet the ow of liquid driven out tangentially by the agitator and serve to assist in breaking up the flow and securing a quiescent surface to the liquid. In Figure l the formation and distribution of air bubbles is indicated by small circles and the distribution of liquid particles by crosses.

In Figure 3 the direction of flow of liquid and Y f liquid.

In the use of this apparatus the air tube I9 is adjusted so that it is spaced above the central disc I6 by an amount which is suillcient to ensure a good working clearance without causing air, sucked down the central tube I9, to bc drawn in to a large extent through the upper blades I1. The liquid is circulated through the upper blades and the bulk of the air is driven into the liquid through the lower blades I5. If this apparatus is used for froth flotation conlcentration the usual reagents are employed, a froth of material to be concentrated collects on the surface of the liquid and overflows over overflow lips 24. The pulp is fed into one of the end vessels of the series and iiows through the openings I2 being treated successively in each vessel. As best seen in Figure 2` the lower air-impelling blades I are -four in number. If desired this number may be increased and although the bottom blades are shown as inclined like the blades of a screw impeller it is to 'oe understood that upright blades may be employed.

Referring now to Figure 4, this shows a simplied form of agitator used in a similar appashrouded above their upper edges by a disc 21. There is a downcast air tube I9 as before. The blades 26 are like the blades I1 of Figure 2 but deeper. Liquid is drawn in by the blades through the space between the outside of the tube I1 and the central aperture in the shield 21 as indicated by arrows 28. Air is drawn in through the same blades below the bottom of the tube I9 as indicated by arrows 29. As before the air enters below the liquid and tends on leaving the agitator to rise into the agitated liquid and becomes thoroughly mixed therewith.

Figure 5 shows a third form in which the agitator comprises a lower disc 30, blades 3l thereon similar to blades I5 in Figure 3, an intermediate disc 32, blades 33 thereon similar to the blades I1 of Figure 3 and an upper shield 34 similar to the shield I8. The air tube I9 is provided as before but the difference is that a cylindrical partition 35 is provided which is supported by and stands up from the disc 32, entering the space between the shaft I3 and the air tube I9. This serves to divide the air passing down thetube I9 into two streams, one of which enters through the lower blades 3i as indicated by the arrows 36 and the other and smaller stream of which passes between the partition 35 and the tube I9 and becomes mixed with the liquid by the blades 33 as indicated by the arrows 31, 38. The space between the partition 35 and the tube I9 is kept to a minimum so as to reduce this latter stream of air and the construction tends to ensure more complete separation between the air, mainly driven in by the bottom blades 3| and the liquid circulated by the upper blades 33.

I claim:

l. In an agitation and aeration apparatus the combinationl of an agitation vessel, a downwardly extending rotatable shaft dipping thereinto, an agitator on the shaft comprising a plurality of liquid-agitating blades and means to support the blades from the shaft so that their inner ends are spaced away from the shaft, a stationary downcast air tube surrounding the shaft with its lower end entering the space inside the inner ends of the blades, and an annular shield above and covering the blades provided with a central aperture surrounding and spaced ratus to that of Figures 1 and 3. In this case s at the bottom of the shaft I 3 there is a disc 25 carrying a number of upstanding blades 26 from the air tube so as to allow a liquid-circula tion space between the edge of the aperture in the shield and the outside of the air tube.

2. Agitation and aeration apparatus as claimed in claim l, wherein a second set of air impelling blades is provided on the agitator below the liquid-agitating blades, to which air-impelling yblades air is delivered from the downcast air tube.

3. In an agitation and aeration apparatus the combination of ,an agitation vessel, a downwardly extending rotatable shaft dipping thereinto, air-impelling blades extending outwardly from the shaft, a disc above the air-impelling blades having a central air-aperture therethrough, liquid agitating blades above the disc, the inner ends of these blades being spaced away from the shaft, an annular shield above the blades the central aperture of which surrounds the shaft and is spaced therefrom and a downcast air tube surrounding the shaft with its lower end passing through the shield so that it enters the space within the blades, the diameter of the air tube being such as to allow a liquid-circulation space between the inner periphery of the shield and the outside of the air tube.

i. Apparatus as claimed in claim 3, wherein the disc which separates the two sets of blades carries an upstanding cylindrical partition which enters the air downcast tube and divides air passing downwardly theretlrough into two streams, one entering the lower blades through the interior of the cylindrical partition and the other entering the upper blades through the space between the outside of the partition and the inside of the air tube and being mixed directly with the liquid at the bottom of the air tube by the upper blades.

5. Agitation and aeration apparatus as claimed in claim 1, wherein the downcast air tube is adjustable for height relatively to the rotatable agitator.

. 6. Agitation and aeration apparatus as claimed in claim 3, wherein the downcast air tube is adjustable for height relatively to the rotatable agitator.

7. Agitation and aeration apparatus as claimed in claim 1, wherein the liquid vessel forms one of a series of flotation pulp vessels for use in the froth flotation process of concentrating minerals.

8. Agitation and aeration apparatus as claimed in claim 3, wherein the liquid vessel forms one of a series of :dotation pulp vessels for use in the froth otation process of concentrating minerals.

' STANLEY TUCKER. 

